Method for operating a double-sided processing machine and double-sided processing machine

ABSTRACT

A method for operating a double-sided processing machine having a top working disk and a bottom working disk which rotate relative to each other and define a working gap between them that is configured for processing flat workpieces is disclosed. The method includes performing a heating step by heating at least the working disks to an operating temperature using a heating apparatus. Then processing the workpieces using one or more processing steps after completion of the heating step.

CROSS REFERENCE TO RELATED INVENTION

This application is based upon and claims priority to, under relevantsections of 35 U.S.C. § 119, German Patent Application No. 10 2021 113131.6, filed May 20, 2021, the entire contents of which are herebyincorporated by reference.

TECHNOLOGICAL FIELD

The following disclosure relates to a method for operating adouble-sided processing machine, in particular a double-sided polishingmachine, which comprises a top working disk and a bottom working diskwhich can be rotated relative to each other by means of a rotary driveand between which a working gap for processing flat workpieces isformed.

The disclosure also relates to a double-sided processing machine, inparticular a double-sided polishing machine, comprising a top workingdisk and a bottom working disk, between which a working gap forprocessing flat workpieces is formed, and comprising a rotary drive withwhich the top working disk and the bottom working disk can be rotatedrelative to each other.

BACKGROUND

In double-sided processing machines, for example double-sided polishingmachines, flat workpieces such as semiconductor wafers are processed,for example polished, in a working gap formed between a top working diskand a bottom working disk. During processing, the working disks arerotated relative to each other by means of a rotary drive. The flatworkpieces can be located, for example, in recesses of what are known asrotor disks which move along a circular path through the working gapduring processing and in doing so rotate about their axis. Theworkpieces are thus guided along cycloidal paths through the working gapand processed. Very high surface qualities of the processed workpieces,in particular very high evenness, can be achieved with such double-sidedprocessing machines. An important parameter for the processing qualityis known to be the GBIR value (Global Backside Ideal Focal Plane Range).

During the in particular material-removing processing of the workpieces,what is known as slurry is often supplied to the working gap. For thispurpose, the top working disk and/or the bottom working disk can havecorresponding supply openings. It is also known, for example, to providethe top working disk and/or the bottom working disk with, for example,labyrinthine tempering channels through which a cooling liquid, forexample water, is conducted during processing in order to keep theworking disks at a specified operating temperature during a processingstep. It is also known to measure the thickness of the processedworkpieces, for example, at multiple radially distanced locations of theworking gap, during a processing step and to terminate the processingstep after a specified target thickness has been reached. For thethickness measurement, various sensors are known, for example, eddycurrent sensors or also optical sensors.

In practice, is has been shown that, in particular after a longerdowntime of a double-sided processing machine, the processing result ofthe first processing runs performed after ending the downtime is not yetoptimal. Thus, for example, a specified GBIR value is regularly onlyreached after multiple processing runs, wherein the number of theprocessing runs required for this seem to depend on the duration of thedowntime of the double-sided processing machine. The workpiecesprocessed during such processing runs until the specified qualitycriteria have been reached have a non-optimal processing result and areaccordingly only usable for lower quality requirements, in particularnot as what are known as prime wafers. If test workpieces are used forthe processing runs required to reach the optimal processing quality,rejects can be avoided. However, this leads to a lower throughput of theprocessing machine and correspondingly higher costs.

Proceeding from the explained prior art, the object of the invention isto provide a method and a double-sided processing machine of the typeexplained above, with which the throughput can be increased compared tothe prior art even after longer downtime of the double-sided processingmachine and the costs can be lowered accordingly.

BRIEF SUMMARY OF THE INVENTION

In an embodiment of the inventive method, at least the working disks areheated to an operating temperature by means of a heating apparatus in aheating step before a processing step is performed. In an embodiment ofthe inventive device, a heating apparatus is provided and is configuredfor heating at least the working disks to an operating temperature in aheating step before a processing step for processing workpieces.

The double-sided processing machine can be, for example, a double-sidedpolishing machine. However, other double-sided processing machines arealso conceivable, for example, double-sided grinding machines ordouble-sided lapping machines. The working disks can each have a workingcovering, for example a polishing pad. The flat workpieces can be, forexample, semiconductor wafers. The top working disk can be fastened to atop support disk. Accordingly, the bottom working disk can be fastenedto a bottom support disk. During processing of workpieces in the workinggap formed between the working disks, they can be rotated relative toeach other. A corresponding rotary drive is provided for this. Forexample, the working disks can be driven to rotate in oppositedirections to each other.

The invention is based on the knowledge that the processing runsdescribed above that are required in order to reach the specifiedprocessing quality correlate with a temperature of the working disksthat is still too low at the beginning In particular after longerdowntime, the working disks and if applicable the support disks can coolbelow the operating temperature. In the course of the processing runsdescribed in the prior art, the working disks are then successivelyheated until they have reached their operating temperature and thespecified processing results have thus been achieved. As also explainedabove, this procedure leads, however, to reduced throughput orrespectively increased costs.

The invention is therefore based on the idea of providing an externalheating apparatus or respectively an external heating source with whichat least the top and bottom working disks are heated before a firstprocessing step to prevent the heating runs described above. Theexternal heating apparatus or respectively external heating source is inthis case provided in addition to the components of the double-sidedprocessing machine provided for the processing of the workpieces and iscorrespondingly not formed by processing workpieces in the working gap.As explained, during such processing, heat is also generated so that,after several heating runs, the working disks reach their operatingtemperature and the processing result thus meets the required criteria.However, according to the invention a heating apparatus is provided thatis separate from this and that achieves a heating of the working diskseven without processing workpieces in the working gap. In particular,during the heating step according to the invention, no workpieces to beprocessed are arranged in the working gap. The heating runs explainedabove are avoided. Accordingly, after the conclusion of the heatingstep, a processing step can directly follow, wherein the workpiecesprocessed hereby already meet the target parameters in the firstprocessing run. The throughput of the double-sided processing machine isincreased accordingly and the costs are reduced. The operatingtemperature of the top working disk and the bottom working disk can be,for example, in a range between 20° C. and 30° C., for example about 25°C.

In addition to the working disks, support disks holding the workingdisks, if provided, can of course also be heated to an operatingtemperature with the heating apparatus. This ensures that the workingdisks can hold their operating temperature at all times.

As explained, after the heating step one or more processing steps forprocessing workpieces in the working gap of the double-sided processingmachine follow. The processing steps comprise in particularmaterial-removing processing of the workpieces, for example, polishing,lapping, or grinding. As explained above, multiple workpieces can bemounted in a floating manner in recesses of what are known as rotordisks for this purpose. The rotor disks move, on one hand, along acircular path through the working gap and, on the other hand, rotateabout their own axis. As a result, the workpieces move along cycloidalpaths through the working gap, whereby an optimal processing result isachieved. The rotor disks can roll, for example, on sprockets on theinner and/or outer edge of the working gap.

The heating step can be controlled or respectively regulated, inparticular initiated and terminated, by a control apparatus and/or aregulation apparatus of the double-sided processing machine. Theregulation apparatus can use in particular the temperature of theheating source and the duration of the heating step as regulationparameters. When the working disks are rotated during the heating step,for example, the rotational speed of the working disks can also be used.Accordingly, the heating step can be controlled or respectivelyregulated by the control apparatus or respectively regulation apparatus.

According to one embodiment, a heated heating liquid is conducted intothe working gap in the heating step. This can be, for example, waterheated by means of a heating source. The heating liquid can have, forexample, a somewhat higher temperature than the desired operatingtemperature, for example 5 to 10° C. higher.

In an embodiment, the heating liquid can be conducted into the workinggap through supply openings for a slurry. As explained above, the topworking disk and/or the bottom working disk can have such supplyopenings for slurry to be supplied to the working gap. The heatingliquid can be conducted into the working gap through these, whereby atthe same time a particularly even distribution of the heating liquid inthe working gap is ensured. The supply openings are designed, forexample, as axial bores in the top working disk and/or the bottomworking disk.

During the heating step, the working disks can be rotated in the samedirection of rotation, in particular in the same direction, furtherparticularly with the same rotational speed, by means of a rotary drive.An even heating of the working disks, in particular of the entire radialextent of the working disks, and if applicable the support disks, canthereby be achieved, wherein the polishing pads are not influenced.However, it is also possible that the working disks are not rotated,meaning stay still, during the heating step.

The working disks can be held during the heating step by spacers betweenthe working disks or by locking a mount of the top and/or the bottomworking disk at a defined distance to each other. This achieves aparticularly defined and effective heating of the working disks and ifapplicable the support disks. The top working disk and/or the bottomworking disk can be settable in height by means of a corresponding mountin order to thus set the working gap in a defined manner. This settingcan be used according to the previous exemplary embodiment in order toensure a defined distance between the working disks during the heatingstep. To lock the working disks, for example, what are known as clampingshoes can be used. However, it is also possible to ensure the defineddistance between the working disks by using suitable spacers between theworking disks. The spacers can be held in the gap, for example, bysetting a narrower gap in the radially outer region of the working gapthan in the radially inner region of the working gap.

According to another embodiment, heated heating liquid can be conductedin the heating step through tempering channels designed in the topworking disk and/or in the bottom working disk. As also explained above,for example, top working disks and/or bottom working disks ofdouble-sided processing machines have tempering channels, through whicha cooling liquid, for example water, is conducted during workpieceprocessing in order to prevent an undesired heating of the working disksduring processing. These, for example labyrinthine, tempering channelsconfigured in the top working disk and/or the bottom working disk can beused in the previous embodiment in a particularly practical manner inthat, during the heating step, a heating liquid heated in a definedmanner is conducted through the tempering channels instead of a coolingliquid and thus the heating of the working disks is realizedeffectively. Of course, it would also be possible for correspondingtempering channels to be designed between the top working disk and a topsupport disk and/or between a bottom working disk and a bottom supportdisk. It would also be conceivable for corresponding tempering channelsto be designed in a top support disk and/or a bottom support disk.Accordingly, the heated heating liquid can also be conducted throughtempering channels designed in this manner.

According to another embodiment, at least the working disks can beheated to an operating temperature in the heating step by means of anelectrical heating apparatus, in particular by means of at least oneelectrical heating mat. Such an electrical heating apparatus, forexample, an electrical heating mat, can be configured, for example, inthe top working disk and/or the bottom working disk, in a top supportdisk and/or a bottom support disk and/or between a top working disk anda top support disk and/or a bottom working disk and a bottom supportdisk. By means of such an electrical heating apparatus, a particularlyfast and defined heating of the working disks can be realized.

According to another embodiment, the temperature of the top working diskand/or the bottom working disk can be measured during the heating step,and the heating step can be terminated after the operating temperaturehas been reached, as determined by the temperature measurement. For thispurpose, temperature sensors, for example, can be configured in the topworking disk and/or the bottom working disk which measure thetemperature of the top working disk and/or the bottom working diskduring the heating step. If the temperature sensors detect that theoperating temperature has been reached, the heating step can beterminated. The heating step can be terminated automatically after theoperating temperature detected in this way has been reached. Thetemperature measurement values of corresponding temperature sensors canbe applied for this purpose to a control and/or regulation apparatus andthe control and/or regulation of the heating step can be based on themaccordingly.

An embodiment of the double-sided processing machine can be configuredto perform the disclosed inventive method. Accordingly, the methodaccording to the invention can be performed with a double-sidedprocessing machine according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is explained in greater detailbelow based on figures. Schematically:

FIG. 1 illustrates a sectional view of an embodiment of a double-sidedprocessing machine; and

FIG. 2 illustrates a diagram of an embodiment of a method of operating adouble-sided processing machine.

The same reference signs refer to the same objects in the figures unlessindicated otherwise.

DETAILED DESCRIPTION OF THE INVENTION

The double-sided processing machine shown in FIG. 1, in which it can be,for example, a double-sided polishing machine, has an annular topworking disk 10 and a likewise annular bottom working disk 12. Betweenthe working disks 10, 12, an annular working gap 14 is formed in whichflat workpieces, for example, semiconductor wafers, can be processed,for example polished. As explained, the workpieces can be mounted in afloating manner in recesses of what are known as rotor disks. The rotordisks can be moved along a circular path through the working gap 14 andin doing so rotate about their own axis. For this purpose, the rotordisks can roll, for example, on sprockets on the inner and/or outer edgeof the working gap 14. This is known per se and is therefore notexplained in more detail.

The top working disk 10 is fastened to a top support disk 16, and thebottom working disk 12 is fastened to a bottom support disk 18. Duringprocessing of workpieces in the working gap 14, the top support disk 16and the bottom support disk 18, and with them the top working disk 10and the bottom working disk 12, are rotated relative to each other aboutan axis of rotation 20 by means of a rotary drive which is not shown inmore detail. For example, the working disks 10, 12 or respectively thesupport disks 16, 18 can be driven to rotate in opposite directions.

In FIG. 1, various further components of the top and bottom workingdisks 10, 12 are shown, wherein they are shown only for one of theworking disks 10, 12 for reasons of clarity. It should be understoodthat the corresponding components, described in more detail in thefollowing, can be configured in both working disks 10, 12.

In the example shown, the top working disk 10 has supply lines 22 forsupplying a slurry to the working gap 14. The supply lines 22 each havesupply openings 23 opening into the working gap 14. In addition, in FIG.1 distance sensors 24, for example, eddy current sensors 24, areprovided in the top working disk 10 and measure the distance to theworkpieces to be processed and thus their thickness at different radiallocations of the working gap 14 during workpiece processing. In FIG. 1,multiple temperature sensors 26 are also designed in the top workingdisk 10, which sensors measure the temperature at least of the topworking disk 10 in particular during a heating step but also, forexample, during a processing step. As explained, temperature sensors canalso be provided in the bottom working disk 12. The same applies to thetop support disk 16 and the bottom support disk 18. In the exampleshown, the measurement results from the temperature sensors 26 areapplied to a control and/or regulation apparatus 28 of the double-sidedprocessing machine. This controls or respectively regulates theoperation of the double-sided processing machine, including a heatingstep still to be explained in the following.

A heating element 30 is also shown schematically in the bottom workingdisk 12. The heating element 30 can be, for example, an electricalheating element 30, for example an electrical heating mat 30. However,the heating element 30 can also be a, for example, labyrinthinearrangement of tempering channels 30 through which heated heating liquidis conducted in a heating step, as will also be explained below. Theheating element 30 can in turn also be configured in the top workingdisk 10. The same applies to the top support disk 16 and the bottomsupport disk 18.

In the method according to the invention, before a processing step isperformed for processing workpieces in the working gap 14, thetemperature of the top working disk 10 and the bottom working disk 12 isfirst brought to a specified operating temperature in a heating step.This can be controlled or respectively regulated by the control and/orregulation apparatus 28. For example, heated heating liquid can beconducted into the working gap 14 in the heating step through the supplylines 22 and the supply openings 23. The working disks 10, 12 and thesupport disks 16, 18 can be rotated in the working gap 14 during thesupply of the heating liquid. During the heating step, the working disks10, 12 can be held at a defined distance from each other, for example bylocking a mount of the top working disk 10 and/or of the bottom workingdisk 12. The temperature sensors 26 can detect when the specifiedoperating temperature has been reached. The control and/or regulationapparatus 28 can then terminate the heating step. Subsequently,workpieces can be processed in one or more processing steps, inparticular material-removing processing, for example, polishing,lapping, or grinding.

Alternatively or additionally, heated heating liquid can be conductedthrough the tempering channels 30 in the heating step and thetemperature of the working disks 10, 12 can thereby be heated to thespecified operating temperature. It is further possible alternatively oradditionally to heat at least the working disks 10, 12 to the operatingtemperature in the heating step by means of the electrical heatingapparatus 30, in particular the heating mat 30. Detecting the operatingtemperature and the corresponding termination of the heating step cantake place, as explained above, by the control and/or regulationapparatus 28. The control and/or regulation apparatus 28 can use thetemperature of the supplied heating liquid, the heating output of theelectrical heating apparatus 30 and the duration of the heating step ascontrol and/or regulation parameters. When the working disks 10, 12 arerotated, the rotational speed of the working disks 10, 12 can also beused.

FIG. 2 shows a diagram with results of a heating according to the priorart and according to the disclosed device/method. The GBIR value isshown normalized in each case over the number of heating runs of thedouble-sided processing machine. The curve 32 refers to the case inwhich the double-sided processing machine was not operated for threenights and days at room temperature and then was used to processworkpieces in processing steps without a heating step according to theinvention. It is shown that three heating runs were required in order toreach a specified GBIR value, which should be as close to 1 as possiblein the normalized version.

The curve 34 describes a case corresponding to the curve 32, wherein thedouble-sided processing machine stood idle, however, for only one nightat room temperature. Here, the number of required heating runs until thedesired GBIR value is reached is shortened to one run. However, acorresponding throughput loss or respectively a corresponding costincrease is still registered.

The curve 36 shows the results for a double-sided processing machinewhich has stood idle for one night at room temperature and in which aheating step according to the invention was performed before the firstprocessing step (run one). The curve 36 shows that the first processingrun here already has the desired GBIR value. Corresponding throughputloss or respectively corresponding cost increases could be avoided.

LIST OF REFERENCE SIGNS

-   10 Top working disk-   12 Bottom working disk-   14 Working gap-   16 Top support disk-   18 Bottom support disk-   20 Axis of rotation-   22 Supply lines-   23 Supply openings-   24 Distance sensors-   26 Temperature sensors-   28 Control and/or regulation apparatus-   30 Heating element-   32 Curve-   34 Curve-   36 Curve

1. A method for operating a double-sided processing machine having a topworking disk and a bottom working disk which rotate relative to eachother and define a working gap between them that is configured forprocessing flat workpieces, the method comprising: performing a heatingstep comprising heating at least the working disks to an operatingtemperature using a heating apparatus; and processing the workpiecesusing one or more processing steps after completion of the heating step.2. The method according to claim 1, further comprising conducting aheated heating liquid into the working gap during the heating step. 3.The method according to claim 2, wherein the conducting of the heatingliquid into the working gap is done through supply openings for aslurry.
 4. The method according to claim 1, rotating the top and bottomworking disks in a same direction during the heating step.
 5. The methodaccording to claim 1, further comprising holding the working disksduring the heating step using one of (1) spacers between the workingdisks and (3) locking a mount of one of the top and bottom working disksat a defined distance from each other.
 6. The method according to claim1, wherein the heating step further comprises conducting a heatedheating liquid through tempering channels positioned in at least one ofthe top working disk and the bottom working disk.
 7. The methodaccording to claim 1, wherein the heating step comprises heating atleast the top and bottom working disks to an operating temperature usingat least one electrical heating mat.
 8. The method according to claim 1,further comprising: measuring a temperature of at least one of the topworking disk and the bottom working disk during the heating step; andterminating the heating step after the operating temperature has beenreached.
 9. A double-sided processing machine comprising: a top workingdisk; a bottom working disk; a working gap configured for processingflat workpieces defined between the top and bottom working disk; and aheating apparatus configured to heat at least one of the top and bottomworking disks to an operating temperature in a heating step, wherein thetop and bottom working disk are configured to rotate relative to eachother, and wherein the heating step is performed before a processingstep for processing the flat workpieces.